1. Field of the Invention
The present invention relates to 5-substituted uridine derivatives which are novel substances and 5'-trityl-5-substituted uridine derivatives which are useful as intermediates for preparing the 5-substituted uridine derivatives. The 5-substituted uridine derivatives of this invention are useful for treating tumors.
2. Description of the Related Art
5-Fluorouridine (hereinafter referred to as "FUR"), which was synthesized in 1959, is known for its excellent activity against malignant tumors (U.S. Pat. No. 2885398). However, FUR has a problem on clinical use because of its high toxicity.
Many attempts have been made to resolve this problem by converting FUR into various derivatives (Japanese Unexamined Patent Publications Nos.64280/1975; 52183/1976; 91997/1982; 246196/1986). However, such attempts failed to give useful derivatives.
5-Trifluoromethyl-2'-deoxyuridine (hereinafter referred to as "F.sub.3 TdR") represented by the formula ##STR2## has an anti-tumor activity [Cancer Research 24, 1979 (1964)] and a strong antiviral activity [Cancer Research 30, 1549, 1970]. In view of these activities, various investigations have been made on the utility of F.sub.3 TdR as pharmaceuticals, but without developing a useful compound.